1. Field of the Disclosure
The present disclosure relates to an organic light emitting diode (OLED) display device and a method for driving the same, which are capable of achieving an enhancement in response characteristics of OLEDs and an enhancement in display picture quality through application of an overdriving (or accelerated driving) method taking into consideration intrinsic response characteristics of OLEDs.
2. Discussion of the Related Art
Recently-highlighted flat panel display devices include a liquid crystal display (LCD) device, a field emission display (FED) device, a plasma display panel (PDP) device, an organic light emitting diode (OLED) display device, etc. Among such flat panel display devices, the OLED display device is usefully applied to mobile communication appliances such as smartphones or tablet computers because it exhibits high brightness, and employs a low drive voltage while having an ultra-slim structure.
Such an OLED display device includes a plurality of pixels, each of which includes an OLED pixel constituted by an anode, a cathode, and an organic light emitting layer interposed between the anode and the cathode, and a pixel circuit for independently driving the OLED pixel. The OLED display device also includes a driving control circuit for independently controlling driving of the pixel circuits of the pixels. Such an OLED display device converts digital data into analog image signals (current or voltage signals), using grayscale-based gamma voltages, and supplies the converted image signals to respective pixel circuits and, as such, an image is displayed through the OLED pixels.
There are conventional OLED display devices or LCD devices employing an overdriving (or accelerated driving) method in which image data to be displayed is modulated in order to reduce response time of pixels. In a conventional overdriving method, image data of a current frame is compared with image data of a previous frame, and the current frame image data is modulated in accordance with a difference between the current frame image data and the previous frame image data.
However, conventional OLED display devices have a limitation in improving response characteristics, using the above-mentioned conventional overdriving method, because OLEDs have intrinsic response characteristics, differently than liquid crystals.
In detail, LCD devices exhibit rapid response characteristics when image conversion is generated from a dark low-grayscale image (0-grayscale) into a bright high-grayscale image (255-grayscale). In such an LCD device, it may be possible to improve response characteristics only through modulation of an image data value into a lower or higher value. However, OLED exhibits very slow response characteristics when image conversion is generated from a dark low-grayscale image (0-grayscale) into a bright high-grayscale image (255-grayscale), differently than liquid crystals. Furthermore, there is a limitation in improving response characteristics of such an OLED through a conventional method of increasing or decreasing an image data value because the response characteristics of the OLED are also influenced by accumulated image data. For example, a data value of about 219-grayscale is required as an overdriving data value for display of an image in a state of being converted from a low-grayscale image (0-grayscale) into an intermediate-grayscale image (112-grayscale). For conversion from a low-grayscale image (0-grayscale) into a high-grayscale image (12-grayscale) having higher grayscale than the intermediate grayscale, however, even a maximum grayscale, namely, 255-grayscale, is insufficient to improve the response characteristics.